This disclosure relates to measurement while drilling (MWD) and, more specifically, a mud pulse telemetry tool and method of use.
MWD is a system to perform drilling related measurements downhole and transmit data to the surface while drilling a well, usually used in the oil and gas industry. Mud pulse telemetry is a common method of data acquisition and transmission used in MWD tools. A downhole valve may operate to restrict the flow of the drilling mud, causing a series of pressure fluctuations that transmit the characteristic information up the wellbore to the surface receiver. The pressure fluctuation propagates via the drilling fluid towards the surface and is received by pressure sensors at or proximal to the earth's surface. The received pressure signals are processed to reconstruct the characteristic information. The pressure fluctuation can be created as a form of a positive pulse, a negative pulse, and a continuous wave. These forms can be generated with an oscillating valve that closes and/or opens to cause drilling fluid pressure to increase and/or decrease. For example, a positive pulse is generated with a brief closure of the valve to restrict the drilling fluid within the drilling pipe to cause an increase of the drilling fluid pressure. A downhole tool/device that generates such mud pulse pressure is referred to in the art as a mud pulser.
In many instances, a high rate mud pulser for downhole telemetry in subterranean wells is desired because higher data transfer rate increases measurement resolution and amount of more detailed formation and directional information to support faster penetration rate. For example, a common sampling rate of 4 bits per second (bps) at a drilling rate of 10 ft/min provides 24 bit/ft, whereas a 40 bps rate at 100 ft/min provides the same data rate per foot drilled. The present disclosure describes a high rate mud pulser that uses a mud powered inertia drive that accelerates the movement of the downhole valve to achieve an increased data rate.